Abstract
Background:
Quadrangular space syndrome (QSS) is a rare condition involving compression of the axillary nerve and/or posterior circumflex humeral artery within the quadrangular space. Neurogenic QSS is caused by entrapment of the axillary nerve due to fibrotic bands, paralabral cysts, trauma, or space-occupying lesions, leading to shoulder pain, weakness, and deltoid atrophy, which is frequently observed in athletes performing overhead activities.
Indications:
A 21-year-old female competitive volleyball player presented with a 5-year history of progressive right arm weakness and shoulder pain, worsened by shoulder activity. The patient's symptoms persisted despite conservative treatments. On examination, she had visible right anterolateral deltoid atrophy and 4/5 weakness with right shoulder forward flexion. Electromyography showed denervation of all 3 deltoid heads with severely decreased motor units, while magnetic resonance imaging demonstrated compression of the right axillary nerve within the quadrangular space and denervation changes of the deltoid muscle. Given the failure of nonsurgical interventions, ongoing symptom progression, and examination findings, axillary nerve decompression was recommended.
Technique Description:
A posterior surgical approach was used for axillary nerve decompression using microsurgical techniques. The patient was positioned supine; a posterior arm incision was made, and the deltoid muscle and the long head of the triceps brachii were exposed and retracted to access the quadrangular space. The teres major fascia was opened to visualize and divide a compressive fibrotic band, completing the nerve decompression.
Results:
The surgery was successful, with significant postoperative improvements. The patient began rehabilitation at 4 weeks postoperatively and experienced restored deltoid muscle mass and strength by the 6-month follow-up, and durable relief at 2 years postoperatively. She achieved a full return to sports.
Discussion/Conclusion:
Axillary nerve decompression proved effective for treating neurogenic quadrangular space syndrome in this case, especially after conservative management had failed. The procedure preserved shoulder function without the need for additional surgical interventions. Return to sports was achievable without complications by 6 months postoperatively. At 2 years postoperatively, the patient continued to have durable relief. The treatment and outcome in this case were consistent with existing literature on this topic, which is Level 4 evidence in the form of case reports and case series.
Patient Consent Disclosure Statement:
The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.
This is a visual representation of the abstract.
Keywords
Video Transcript
Today I am going to discuss a case of axillary nerve decompression for neurogenic quadrangular space syndrome.
Background
This case covers a 21-year-old female athlete with neurogenic quadrangular space syndrome confirmed by examination and imaging. The patient opted for axillary nerve decompression surgery, which was successful. She began rehabilitation 4 weeks postoperatively, fully recovering by 5 months postoperatively.
INDICATIONS
Our patient is a 21-year-old female competitive volleyball player with a history of progressive right arm weakness and pain worse with activity, localized to the right shoulder, that has been progressive for 5 years. On examination, the patient has visible right anterolateral deltoid atrophy and mild subluxation with anterior load and shift. On resisted forward flexion of the right shoulder, she has 4/5 weakness and anteriorly located right shoulder pain. She is otherwise fully strong, with 2+ reflexes throughout and no sensory deficits.
On neuroimaging, magnetic resonance imaging demonstrates marked right deltoid atrophy and compression, resulting in increased signal and swelling of the axillary nerve distally within the quadrangular space. Those imaging results are further shown here.
On electrodiagnostic workup, the patient has right axillary neuropathy with active and chronic denervation, with the anterior deltoid being more affected than the middle and posterior deltoid. There is no involvement in the teres minor or other muscles.
In this case, the patient had previously attempted conservative management with rest, a change in training regimen, and therapy, although these did not improve her symptoms. Given her progression and failure of conservative management, surgical treatment was recommended. Treatment was offered via axillary nerve decompression at the right quadrangular space via a posterior approach.
The risks and benefits of the procedure were discussed with the patient.
Alternative surgeries were also discussed—including conservative management, such as activity modification, physical therapy, and nonsteroidal anti-inflammatory drug use. However, given the patient's prior attempts at these, the decision was made to pursue surgery.
Surgical alternatives include nerve transfer and deltoid reanimation with a muscle or tendon transfer. Both were discussed, but the patient opted not to pursue these due to her adequate compensation and full range of motion.
Technique Description
The patient was positioned supine with her right arm raised and supported over her face. Pressure points were padded, and the eyes were checked to ensure they were free of compression. A line was marked from the olecranon to a point 2 cm below the spine of the scapula, and a dashed line was made along the inferior border of the deltoid. Some surgeons may find nerve stimulation useful.
The skin and subcutaneous tissue are dissected, exposing the deltoid muscle and the long head of the triceps brachii. The triceps brachii long head is then retracted to allow a view into the quadrangular space.
The deltoid was mobilized and reflected to expose the quadrangular space. The intersection of the axillary nerve as it entered the deltoid fascia was next identified, and the nerve was followed into the quadrangular space. The distal quadrangular space was identified with the axillary nerve exiting past the teres major muscle border. The fascia of the teres major was opened, and a small portion of the teres major muscle was divided to improve visualization of the axillary nerve and quadrangular space. The distal teres major muscle was retracted to expose deeper within the quadrangular space. A severely compressive muscular band of the teres major was identified at the proximal quadrangular space and sharply divided, which resulted in axillary nerve decompression.
After this decompression, the fat pad of the infraclavicular brachial plexus was visualized, and the axillary nerve was verified to be free of compression, proximal and distal to the quadrangular space.
Discussion
Now I am going to go into the background of the quadrangular space syndrome, which includes injury to the contents of the quadrangular space, such as the axillary nerve and posterior circumflex humoral artery. Injury is often the result of compression due to fibrotic bands entrapping the nerve or a space-occupying lesion.1,2
The quadrangular space is bordered superiorly by the teres minor, inferiorly by the teres major, medially by the triceps brachii long head, and laterally by the surgical neck of the humerus. Contents include the axillary nerve and posterior circumflex humoral artery.1,2
The axillary nerve itself divides within the quadrangular space into an anterior branch, which innervates the anterior two-thirds of the deltoid, and a posterior branch, which innervates the posterior one-third of the deltoid and teres minor. The superior lateral brachial cutaneous nerve also originates from the axillary nerve.1,2
Symptoms of neurogenic quadrangular space syndrome include weakness and fatigue of shoulder abduction and external rotation resulting from damage to the innervation of the deltoid and teres minor with subsequent atrophy. Focal pain in the upper limb may also occur.
Most cases involve athletes and active individuals participating in sports with overhead components.1,2
Differential diagnosis may include suprascapular nerve entrapment, Parsonage-Turner syndrome, thoracic outlet syndrome, and cervical disc pathology.1,2
Results and Conclusion
Returning to the case, this patient was discharged home on ibuprofen for pain control. She began physical therapy and working with athletic trainers at 4 weeks postoperatively.
At the 3-month follow-up point, she endorsed improved strength and reduced pain. She was advised to slowly ease into sport while avoiding severe strength training, particularly of the external rotators.
At 6-month follow-up, the patient endorsed return of deltoid muscle mass and full return to sports without pain, numbness, or tingling. At 2 years postoperatively, the patient continued to have durable symptom relief. No other follow-up imaging was obtained.
Footnotes
The authors declared that they have no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto. The University of Michigan Medical School Institutional Review Board deemed this study exempt (ID No. HUM00234765) per exemption 4(iii) at 45 CRF 46.104(d). Written informed consent was obtained from the patient.
